Myeloma is a neoplastic condition which appears to be restricted to mouse and man. The abnormal cells produce large amounts of immunoglobulin-like proteins. One may obtain large homogeneous populations of neoplastic cells producing predominantly a single protein species. Such cells offer many advantages for the study of both neoplasma and immunoglobulin synthesis. This study will concentrate on the messenger RNA (mRNA) and heterogeneous nuclear RNA (HnRNA) of human and murine myelomas. Murine myelomas will be grown in animals; cell lines of human myelomas are available. HnRNA and mRNA will be isolated by standard methods. New methods are being devised to isolate that fraction of the HnRNA that is the precursor of the messenger RNA. It is assumed that the bulk of the polyribosome-bound mRNA is message for the predominant myeloma protein. This point will be investigated by protein-synthetic experiments. The transport and processing of the mRNA from nucleus to cytoplasm will be investigated using molecular hybridization. The relative amounts of specific mRNA and precursor HnRNA will be measured in order to clarify the precursor-product relationship. Attempts will be made to identify HnRNA sequences common to various myelomas. The effects of selected drugs on the processes studied will be investigated.